U.S. patent number 6,830,317 [Application Number 10/419,839] was granted by the patent office on 2004-12-14 for ink jet recording head.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Mineo Kaneko, Masaki Oikawa, Keiji Tomizawa, Ken Tsuchii, Keiichiro Tsukuda, Kenji Yabe.
United States Patent |
6,830,317 |
Tsuchii , et al. |
December 14, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Ink jet recording head
Abstract
In an ink jet recording head from which a small ink droplet and
a large ink droplet can be discharged, a common liquid chamber is
connected to discharge ports via ink flow paths and pressure
chambers, and ink droplets are discharged from the discharge ports
by utilizing thermal energy of heaters. Widths of the ink flow
paths are narrower than widths of the pressure chambers so that the
ink flow paths act as restriction portions. If it is assumed that a
sectional area of the small liquid droplet ink flow path is
S.sub.S, a sectional area of the small liquid droplet pressure
chamber is S.sub.RS, a sectional area of the large liquid droplet
ink flow path is S.sub.L and a sectional area of the large liquid
droplet pressure chamber is S.sub.RL, a relationship S.sub.S
/S.sub.RS <S.sub.L /S.sub.RL is established.
Inventors: |
Tsuchii; Ken (Kanagawa,
JP), Kaneko; Mineo (Tokyo, JP), Tsukuda;
Keiichiro (Kanagawa, JP), Oikawa; Masaki (Tokyo,
JP), Yabe; Kenji (Kanagawa, JP), Tomizawa;
Keiji (Kanagawa, JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
28786773 |
Appl.
No.: |
10/419,839 |
Filed: |
April 22, 2003 |
Foreign Application Priority Data
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Apr 23, 2002 [JP] |
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2002-121209 |
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Current U.S.
Class: |
347/56;
347/43 |
Current CPC
Class: |
B41J
2/1404 (20130101); B41J 2/2125 (20130101); B41J
2/15 (20130101); B41J 2002/14403 (20130101); B41J
2002/14387 (20130101); B41J 2002/14475 (20130101) |
Current International
Class: |
B41J
2/15 (20060101); B41J 2/14 (20060101); B41J
2/145 (20060101); B41J 2/21 (20060101); B41J
002/05 () |
Field of
Search: |
;347/63,65,67,48,20,56,61,15,45,47,43,92 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 719 647 |
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Jul 1996 |
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EP |
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1 186 414 |
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Mar 2002 |
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EP |
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2002-178520 |
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Jun 2002 |
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JP |
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Primary Examiner: Feggins; K.
Assistant Examiner: Do; An H.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. An ink jet recording head in which a plurality of pressure
chambers are connected to a plurality of ink flow paths branched
from a common liquid chamber, respectively, and a plurality of
discharge ports are communicated with said plurality of pressure
chambers, respectively, and a plurality of electro-thermal
converting elements are disposed within said plurality of pressure
chambers, respectively, and inks supplied from said common liquid
chamber to said pressure chambers can be discharged from said
discharge ports by pressure generated in said pressure chambers by
utilizing heat generated by said electro-thermal converting
elements, wherein said plurality of pressure chambers include a
small liquid droplet pressure chamber for discharging a small
liquid droplet and a large liquid droplet pressure chamber for
discharging a large liquid droplet, and regarding said ink flow
path for discharging a small liquid droplet connected to said small
liquid droplet pressure chamber, said small liquid droplet pressure
chamber, said ink flow path for discharging a large liquid droplet
connected to said large liquid droplet pressure chamber, and said
large liquid droplet pressure chamber, when a section substantially
perpendicular to ink flows directed from said respective ink flow
paths to said respective pressure chambers is considered, a
relationship between a sectional area S.sub.S of said small liquid
droplet ink flow path, a sectional area S.sub.RS of said small
liquid droplet pressure chamber, a sectional area S.sub.L of said
large liquid droplet ink flow path, and a sectional area S.sub.RL
of said large liquid droplet pressure chamber satisfies S.sub.S
/S.sub.RS <S.sub.L /S.sub.RL.
2. An ink jet recording head according to claim 1, wherein a
relationship between the sectional area S.sub.RS of said small
liquid droplet pressure chamber and the sectional area S.sub.RL of
said large liquid droplet pressure chamber and an ink amount
I.sub.S of the small liquid droplet discharged from said small
liquid droplet pressure chamber and an ink amount I.sub.L of the
large liquid droplet discharged from said large liquid droplet
pressure chamber satisfies S.sub.RS /S.sub.RL >I.sub.S
/I.sub.L.
3. An ink jet recording head according to claim 2, wherein
1.gtoreq.S.sub.RS /S.sub.RL.gtoreq.0.5 is satisfied.
4. An ink jet recording head according to claim 3, wherein
1.gtoreq.S.sub.RS /S.sub.RL.gtoreq.0.7 is satisfied.
5. An ink jet recording head according to claim 1, wherein a
relationship between a volume V.sub.RS of said small liquid droplet
pressure chamber and a volume V.sub.RL of said large liquid droplet
pressure chamber and an ink amount I.sub.S of the small liquid
droplet discharged from said small liquid droplet pressure chamber
and an ink amount I.sub.L of the large liquid droplet discharged
from said large liquid droplet pressure chamber satisfies V.sub.RS
/V.sub.RL >I.sub.S /I.sub.L.
6. An ink jet recording head according to claim 5, wherein
1.gtoreq.V.sub.RS /V.sub.RL.gtoreq.0.3 is satisfied.
7. An ink jet recording head according to claim 6, wherein
1.gtoreq.V.sub.RS /V.sub.RL.gtoreq.0.5 is satisfied.
8. An ink jet recording head according to claim 1, wherein the
sectional area S.sub.RS of said small liquid droplet pressure
chamber is substantially the same as the sectional area S.sub.RL of
said large liquid droplet pressure chamber.
9. An ink jet recording head according to claim 8, wherein
1.gtoreq.S.sub.RS /S.sub.RL.gtoreq.0.9 is satisfied.
10. An ink jet recording head according to claim 8, wherein S.sub.L
=S.sub.RL and S.sub.S <S.sub.RS are satisfied.
11. An ink jet recording head according to claim 1, wherein a
volume V.sub.RS of said small liquid droplet pressure chamber is
substantially the same as a volume V.sub.RL of said large liquid
droplet pressure chamber.
12. An ink jet recording head according to claim 11, wherein
1.gtoreq.V.sub.RS /V.sub.RL.gtoreq.0.8 is satisfied.
13. An ink jet recording head according to claim 1, wherein the
following relationships are satisfied:
S.sub.Lb =R.sub.Lf /(R.sub.Lf +R.sub.Lb).times.S.sub.Le
where, S.sub.Lb : flow resistance of large liquid droplet side;
S.sub.Sb : flow resistance of small liquid droplet side; R.sub.Lf :
flow resistance from electro-thermal converting element of large
liquid droplet pressure chamber to corresponding discharge port;
R.sub.Lb : flow resistance from electro-thermal converting element
of large liquid droplet ink flow path to common liquid chamber;
S.sub.Le : effective bubbling area of large liquid droplet
electro-thermal converting element; R.sub.Sf : flow resistance from
electro-thermal converting element of small liquid droplet pressure
chamber to corresponding discharge port; R.sub.Sb : flow resistance
from electro-thermal converting element of small liquid droplet ink
flow path to common liquid chamber; and S.sub.Se : effective
bubbling area of small liquid droplet electro-thermal converting
element.
14. An ink jet recording head according to claim 13, wherein
S.sub.Lb.ltoreq.S.sub.Sb <1.59 S.sub.Lb is satisfied.
15. An ink jet recording head according to claim 13, wherein the
following relationships are satisfied: ##EQU17##
D(x)=12.0.times.(0.33+1.02.times.(a(x)/b(x)+b(x)/a(x)))
where, R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; D(x):
section coefficient of ink flow path at position of distance x;
a(x): height of ink flow path at position of distance x; b(x):
width of ink flow path at position of distance x; and .eta.: ink
viscosity, and, ##EQU18##
D(y)=12.0.times.(0.33+1.02.times.(c(y)/d(y)+d(y)/c(y)))
where, R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from common liquid chamber; S(y): sectional area of ink
flow path at position of distance y; D(y): section coefficient of
ink flow path at position of distance y; c(y): height of ink flow
path at position of distance y; and d(y): width of ink flow path at
position of distance y.
16. An ink jet recording head according to claim 15, wherein the
flow resistance R.sub.f is a flow resistance of said discharge
port.
17. An ink jet recording head according to claim 13, wherein the
following relationships are satisfied: ##EQU19##
D(x.sub.n)=12.0.times.(0.33+1.02.times.(a(x.sub.n)/b(x.sub.n)+b(x.sub.n)/
a(x.sub.n)))
where, R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n): sectional area of ink flow
path at position of x.sub.n ; D(x.sub.n): section coefficient of
ink flow path at position of x.sub.n ; a(x.sub.n): height of ink
flow path at position of x.sub.n ; b(x.sub.n): width of ink flow
path at position of x.sub.n ; and .eta.: ink viscosity, and,
##EQU20##
D(y.sub.n)=12.0.times.(0.33+1.02.times.(c(y.sub.n)/d(y.sub.n)+d(y.sub.n)/
c(y.sub.n)))
where, R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; S(y.sub.n): sectional area of ink flow path at position
of y.sub.n ; D(y.sub.n): section coefficient of ink flow path at
position of y.sub.n ; c(y.sub.n): height of ink flow path at
position of y.sub.n ; and d(y.sub.n): width of ink flow path at
position of y.sub.n.
18. An ink jet recording head according to claim 17, wherein, in
said small liquid droplet ink flow path, the following relationship
is satisfied:
where, S.sub.e : effective bubbling area of electro-thermal
converting element.
19. An ink jet recording head according to claim 18, wherein, in
said small liquid droplet ink flow path, the following relationship
is satisfied:
20. An ink jet recording head according to claim 13, wherein the
following relationships are satisfied: ##EQU21##
where, R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; and
.rho.: ink density, and, ##EQU22##
where, R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from the common liquid chamber; and S(y): sectional area
of ink flow path at position of distance y.
21. An ink jet recording head according to claim 13, wherein the
following relationships are satisfied: ##EQU23##
where, R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n): sectional area of ink flow
path at position of x.sub.n ; and .eta.: ink viscosity, and,
##EQU24##
where, R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; and S(y.sub.n): sectional area of ink flow path at
position of y.sub.n.
22. An ink jet recording head according to claim 1, wherein an ink
amount of the small liquid droplet is below 4 pl.
23. An ink jet recording head according to claim 1, wherein
distances between said discharge ports and said electro-thermal
converting elements, respectively, are substantially the same as
each other regardless of a size of the ink droplet to be
discharged.
24. An ink jet recording head according to claim 1, wherein said
plurality of discharge ports are formed in the same substrate
regardless of a size of the ink droplet to be discharged.
25. An ink jet recording head according to claim 1, wherein, at one
side of said common liquid chamber, only said ink flow paths,
pressure chambers and discharge ports for discharging ink droplets
having the same size are connected side by side.
26. An ink jet recording head according to claim 1, wherein, at one
side of said common liquid chamber, only said ink flow paths,
pressure chambers and discharge ports for discharging ink droplets
having different sizes are connected alternately side by side.
27. An ink jet recording head according to claim 1, wherein a
nozzle filter is disposed between said ink flow paths and said
common liquid chamber.
28. An ink jet recording head according to claim 27, wherein said
nozzle filter provided between said small liquid droplet ink flow
path and said common liquid chamber is greater than said nozzle
filter provided between said large liquid droplet ink flow path and
said common liquid chamber.
29. An ink jet recording head according to claim 1, wherein a
driving pulse width Pw of said electro-thermal converting elements
driven within said pressure chambers, respectively, is smaller than
1.4 .mu.s.
30. An ink jet recording head according to claim 29, wherein the
driving pulse width Pw of said electro-thermal converting elements
is smaller than 1.2 .mu.s.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head for
performing recording by discharging an ink droplet from a discharge
port and by adhering the ink droplet onto a recording medium.
2. Related Background Art
As one of the ink discharging methods in ink jet recording
apparatuses, which are now used widely, there is a method utilizing
an electro-thermal converting element (heater). The principle is
that heat is generated by applying an electrical signal to the
electro-thermal converting element disposed in a pressure chamber
to which ink is supplied, thereby heating the ink near the
electro-thermal converting element instantaneously to boil the ink,
with the result that the ink is discharged from a discharge port
externally by great bubble pressure abruptly generated due to phase
change. An ink jet recording head of this type has advantages that
the structure is simple and that integration of ink flow paths is
facilitated.
In such an ink jet recording head, there is a case where recording
is performed by forming an ink droplet finer than the normal ink
droplet in order to realize highly fine recording. To this end,
there has been proposed an arrangement in which the discharging of
the larger ink droplet and the discharging of the smaller ink
droplet are used properly. In general, it can be considered that
the discharge port and the electro-thermal converting element must
be miniaturized in order to discharge the smaller ink droplet.
Concretely, in order to reduce the size of the discharged liquid
droplet, the discharge port area is made smaller substantially in
inverse proportion to the discharge amount. For example, when an
ink droplet of 5 pl is preferably discharged from a discharge port
having a diameter of 16 to 16.5 .mu.m (area is 201 to 214
.mu.m.sup.2), it is considered to be preferable that a discharge
port for discharging a smaller ink droplet (for example, 4 pl) has
a diameter of about 15.5 .mu.m (area is 189 .mu.m.sup.2) and a
discharge port for discharging a more smaller ink droplet (for
example, 2 pl) has a diameter of about 10.5 .mu.m (area is 87
.mu.m.sup.2).
According to a normal design method, when the discharge port and
the electro-thermal converting element are miniaturized in order to
discharge the small ink droplet, the pressure chamber within which
the electro-thermal converting element is installed is also
miniaturized accordingly. An ink flow path for connecting the
pressure chamber to a common liquid chamber is designed to have a
width the same as the width of the pressure chamber. That is to
say, in correspondence to the miniaturization of the ink droplet,
the discharge port, electro-thermal converting element and pressure
chamber are all miniaturized at the same rate, and the pressure
chamber and the ink flow path are formed to have the same
width.
However, in such a design method, it was found that there is a case
where the minute ink droplet may not be discharged successfully.
That is to say, even if a small liquid discharging nozzle is
constructed by reducing the dimensions of the discharge port,
electro-thermal converting element and pressure chamber which can
discharge the normal ink droplet (large ink droplet) successfully
in proportion to the reduction of the ink amount of the ink droplet
to be discharged, in many cases, good ink droplet discharging
cannot be achieved. It is guessed that one of factors causing the
poor discharging is the fact that flow resistance is increased by
the miniaturization of the discharge port.
Explaining this more concretely, the viscosity resistance of the
discharge port is increased in inverse proportion to fourth power
of the area of the discharge port. That is to say, when the
discharge port is miniaturized in correspondence to the
miniaturization of the ink droplet, since the viscosity resistance
is increased, in order to maintain the proper discharging condition
if the viscosity resistance is increased, the bubbling power
generated by the electro-thermal converting element must be
increased. In the above-mentioned conventional design method,
although it was considered that the bubbling power of the
electro-thermal converting element can merely be decreased in
accordance with the miniaturization of the discharged ink droplet,
actually, it is considered that, in addition to this, bubbling
power required for is overcoming the increased viscosity resistance
should be considered. Accordingly, the minimum bubbling power
required for discharging the ink droplet from the discharge port
successfully cannot eventually be reduced much in comparison with
the case where the large ink droplet is discharged, because the
fact that the power can be reduced in accordance with the
miniaturization of the ink droplet to be discharged is cancelled
out by the fact that the power must be increased to cope with the
increase in viscosity resistance, with the result that the size of
the electro-thermal converting element cannot be reduced much.
Further, due to limitation of the design of the ink jet recording
head, in a certain case, the distance between the electro-thermal
converting element and the discharge port cannot be shortened in
accordance with the miniaturization of the ink droplet to be
discharged and the discharge port. That is to say, there is a case
where the distance between the electro-thermal converting element
and the discharge port becomes constant by forming the discharge
port for discharging the large ink droplet and the discharge port
for discharging the small ink droplet in a single substrate and
installing the corresponding electro-thermal converting elements in
parallel on the single substrate in order to simplify the
construction and the manufacturing process. In this case, even when
the diameter of the discharge port is decreased in accordance with
the miniaturization of the ink droplet to be discharged, the
distance to the discharge port cannot be shortened, thereby causing
bad balance. Since the distance to the discharge port is long
relatively, the energy required for discharging the ink out of the
discharge port becomes relatively great.
Also for this reason, the minimum energy required for discharging
the ink droplet cannot be reduced much in comparison with the rate
of reduction of the amount of the ink droplet and the rate of the
miniaturization of the discharge port, and the size of the
electro-thermal converting element cannot be reduced much in
comparison with the electro-thermal converting element for
discharging the large ink droplet.
For example, in the above-mentioned example, if the electro-thermal
converting element used for discharging the ink droplet of 5 pl has
a square shape of 26 .mu.m.times.26 .mu.m (or two elements having a
dimension of 12.5 .mu.m.times.28 .mu.m), the electro-thermal
converting element for discharging the ink droplet of 4 pl is
required to have a square shape of about 24 .mu.m.times.24 .mu.m,
and, the electro-thermal converting element required for
discharging the ink droplet of 2 pl becomes a square shape of about
22 .mu.m.times.22 .mu.m (or two elements having a dimension of
about 11.5 .mu.m.times.27 .mu.m). As such, while the discharge port
can be miniaturized in accordance with the reduction of the
dimensions of the ink droplet, in comparison with this, the
electro-thermal converting element cannot be miniaturized so
much.
Further, the pressure chamber for discharging the small ink droplet
cannot be miniaturized so much since it must contain the
electro-thermal converting element. When a margin of 2 .mu.m is
provided around an outer periphery of the electro-thermal
converting element in consideration of alignment error of a flow
path forming member, for example, the pressure chamber required for
discharging the ink droplet of 5 pl must have a square shape of
(26+4) .mu.m.times.(26+4) .mu.m=30 .mu.m.times.30 .mu.m (bottom
area is 900 .mu.m.sup.2) or a square shape of (12.5.times.2+3+4)
.mu.m.times.(28+4) .mu.m=32 .mu.m.times.32 .mu.m (bottom area is
1,024 .mu.m.sup.2). In contrast, the pressure chamber required for
discharging the ink droplet of 4 pl has a square shape of (24+4)
.mu.m.times.(24+4) .mu.m=28 .mu.m.times.28 .mu.m (bottom area is
784 .mu.m.sup.2), and the pressure chamber required for discharging
the ink droplet of 2 pl has a square shape of (22+4)
.mu.m.times.(22+4) .mu.m=26 .mu.m.times.26 .mu.m (bottom area is
676 .mu.m.sup.2) or a rectangular shape of (11.5.times.2+3+4)
.mu.m.times.(27+4) .mu.m=30 .mu.m.times.31 .mu.m (bottom area is
930 .mu.m.sup.2).
As such, when the minute ink droplet is discharged, the
electro-thermal converting element and the pressure chamber cannot
be miniaturized so much in comparison with the rate of the
miniaturization of the discharge port.
As mentioned above, since an ink flow path having the same width of
that of the pressure chamber is normally provided, when the
pressure chamber is not miniaturized so much, the width of the ink
flow path is not reduced so much. As a result, of the bubbling
power of the electro-thermal converting eminent, a power component
directed toward the ink flow path side rather than the discharge
port side and not contributing to the discharging of the ink
droplet is increased so as to cause great loss, thereby worsening
the energy efficiency.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an
ink jet recording head in which loss can be reduced and energy
efficiency can be enhanced also in a nozzle for discharging a small
ink droplet, on the basis of a unique designing method, which is
unknown in the prior art.
The present invention provides an ink jet recording head in which
pressure chambers are connected to a plurality of respective ink
flow paths branched from a common liquid chamber, discharge ports
are communicated with the respective pressure chambers, ink
supplied from the common liquid chamber to each pressure chamber
can be discharged from the corresponding discharge port by pressure
generated in the pressure chamber by heat from a corresponding
electro-thermal converting element, and wherein the plurality of
pressure chambers include a small liquid droplet pressure chamber
for discharging a small liquid droplet and a large liquid droplet
pressure chamber for discharging a large liquid droplet, and,
regarding the ink flow path for the small liquid droplet connected
to the small liquid droplet pressure chamber, the small liquid
droplet pressure chamber, the ink flow path for the large liquid
droplet connected to the large liquid droplet pressure chamber and
the large liquid droplet pressure chamber, when sections
substantially perpendicular to ink flows directed from the
respective ink flow paths to the respective pressure chambers are
looked at, a relationship between a sectional area S.sub.S of the
small liquid droplet ink flow path, a sectional area S.sub.RS of
the small liquid droplet pressure chamber, a sectional area S.sub.L
of the large liquid droplet ink flow path and a sectional area
S.sub.RL of the large liquid droplet pressure chamber satisfies
S.sub.S /S.sub.RS <S.sub.L /S.sub.RL. Further, it is preferable
that a relationship between the sectional area S.sub.RS of the
small liquid droplet pressure chamber and the sectional area
S.sub.RL of the large liquid droplet pressure chamber and an ink
amount I.sub.S of the small liquid droplet discharged from the
small liquid droplet pressure chamber and an ink amount I.sub.L of
the large liquid droplet discharged from the large liquid droplet
pressure chamber satisfies S.sub.RS /S.sub.RL >I.sub.S
/I.sub.L.
Further, it is preferable that a relationship between a volume
V.sub.RS of the small liquid droplet pressure chamber and a volume
V.sub.RL of the large liquid droplet pressure chamber and the ink
amount I.sub.S of the small liquid droplet discharged from the
small liquid droplet pressure chamber and the ink amount I.sub.L of
the large liquid droplet discharged from the large liquid droplet
pressure chamber satisfies V.sub.RS /V.sub.RL >I.sub.S
/I.sub.L.
Further, S.sub.L =S.sub.RL and S.sub.S <S.sub.RS may be
satisfied.
Further, it is preferable that the following relationships are
satisfied:
where S.sub.Lb : flow resistance of large liquid droplet side;
S.sub.Sb : flow resistance of small liquid droplet side; R.sub.Lf :
flow resistance from electro-thermal converting element of large
liquid droplet pressure chamber to corresponding discharge port;
R.sub.Lb : flow resistance from electro-thermal converting element
of large liquid droplet ink flow path to common liquid chamber;
S.sub.Le : effective bubbling area of the large liquid droplet
electro-thermal converting element; R.sub.Sf : flow resistance from
electro-thermal converting element of small liquid droplet pressure
chamber to corresponding discharge port; R.sub.Sb : flow resistance
from electro-thermal converting element of small liquid droplet ink
flow path to common liquid chamber; and S.sub.Se : effective
bubbling area of small liquid droplet electro-thermal converting
element.
Further, the following relationships or equations may be satisfied:
##EQU1##
D(x)=12.0.times.(0.33+1.02.times.(a(x)/b(x)+b(x)/a(x)))
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; D(x):
section coefficient of ink flow path at position of distance x;
a(x): height of ink flow path at position of distance x; b(x):
width of ink flow path at position of distance x; and .eta.: ink
viscosity, and, ##EQU2##
D(y)=12.0.times.(0.33+1.02.times.(c(y)/d(y)+d(y)/c(y)))
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from the common liquid chamber; S(y): sectional area of
ink flow path at position of distance y; D(y): section coefficient
of ink flow path at position of distance y; c(y): height of ink
flow path at position of distance y; and d(y): width of ink flow
path at position of distance
Further, the following relationships may be satisfied: ##EQU3##
D(x.sub.n)=12.0.times.(0.33+1.02.times.(a(x.sub.n)/b(x.sub.n)+b(x.sub.n)/
a(x.sub.n)))
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n) sectional area of ink flow
path at position of x.sub.n ; D(x.sub.n): section coefficient of
ink flow path at position of x.sub.n ; a(x.sub.n): height of ink
flow path at position of x.sub.n ; b(x.sub.n): width of ink flow
path at position of x.sub.n ; and .eta.: ink viscosity, and,
##EQU4##
D(y.sub.n)=12.0.times.(0.33+1.02.times.(c(y.sub.n)/d(y.sub.n)+d(y.sub.n)/
c(y.sub.n)))
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; S(y.sub.n): sectional area of ink flow path at position
of y.sub.n ; D(y.sub.n): section coefficient of ink flow path at
position of y.sub.n ; c(y.sub.n): height of ink flow path at
position of y.sub.n ; and d(y.sub.n): width of ink flow path at
position of y.sub.n.
Further, the following relationships may be satisfied: ##EQU5##
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; and
.rho.: ink density, and, ##EQU6##
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from the common liquid chamber; and S(y): sectional area
of ink flow path at position of distance y.
Further, the following relationships may be satisfied: ##EQU7##
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n): sectional area of ink flow
path at position of x.sub.n ; and .eta.: ink viscosity, and,
##EQU8##
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; and S(y.sub.n): sectional area of ink flow path at
position of y.sub.n.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic plan view showing a fundamental construction
of an ink jet recording head according to a first reference
example, and FIG. 1B is a sectional view thereof;
FIG. 2A is an enlarged plan view showing a main part of the ink jet
recording head according to the first reference example shown in
FIG. 1A with part of the structure omitted, and FIG. 2B is a
sectional view taken along the line 2B--2B;
FIG. 3A is an enlarged plan view showing a main part of an ink jet
recording head according to a second reference example with part of
the structure omitted, and FIG. 3B is a sectional view taken along
the line 3B--3B;
FIG. 4A is an enlarged plan view showing a main part of an ink jet
recording head according to a first embodiment of the present
invention with part of the structure omitted, and FIG. 4B is a
sectional view taken along the line 4B--4B;
FIG. 5A is an enlarged plan view showing a main part of an ink jet
recording head according to a second embodiment of the present
invention with part of the structure omitted, and FIG. 5B is a
sectional view taken along the line 5B--5B;
FIG. 6A is an enlarged plan view showing a main part of an ink jet
recording head according to a third reference example with part of
the structure omitted, and FIG. 6B is a sectional view taken along
the line 6B--6B;
FIG. 7A is an enlarged plan view showing a main part of an ink jet
recording head according to a fourth reference example with part of
the structure omitted, and FIG. 7B is a sectional view taken along
the line 7B--7B;
FIG. 8A is an enlarged plan view showing a main part of an ink jet
recording head according to a third embodiment of the present
invention with part of the structure omitted, and FIG. 8B is a
sectional view taken along the line 8B--8B;
FIG. 9A is an enlarged plan view showing a main part of an ink jet
recording head according to a fourth embodiment of the present
invention with part of the structure omitted, and FIG. 9B is a
sectional view taken along the line 9B--9B; and
FIG. 10A is an enlarged plan view showing a main part of an ink jet
recording head according to a fifth embodiment of the present
invention with part of the structure omitted, and FIG. 10B is a
sectional view taken along the line 10B--10B.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, embodiments of the present invention and reference examples
will be explained with reference to the accompanying drawings.
First Reference Example
An ink jet recording head according to a first reference example is
shown in FIGS. 1A and 1B and FIGS. 2A and 2B. As shown in FIGS. 1A
and 1B, in a fundamental construction of the ink jet recording
head, five ink supply ports 2 are formed in a single substrate 1,
and cyan ink is supplied to the ink supply ports 2A and 2E, magenta
ink is supplied to the ink supply ports 2B and 2D and yellow ink is
supplied to the ink supply port 2C. A discharge port plate 9 to be
joined to the substrate 1 is provided with large liquid droplet
discharge ports 3a for discharging large liquid droplets and small
liquid droplet discharge ports 3b for discharging small liquid
droplets with respect to the respective ink supply ports 2.
Regarding the ink supply ports 2A and 2B, the large liquid droplet
discharge ports 3a are disposed at a left side in FIGS. 1A and 1B
and small liquid droplet discharge ports 3b are disposed at a right
side in FIGS. 1A and 1B. Regarding the ink supply ports 2D and 2E,
the small liquid droplet discharge ports 3b are disposed at a left
side in FIGS. 1A and 1B and the large liquid droplet discharge
ports 3a are disposed at a right side in FIGS. 1A and 1B, and,
regarding the ink supply port 2C, the large ink droplet discharge
ports 3a are disposed on both sides. Accordingly, if the substrate
1 is shifted in either direction along an arrangement direction of
the ink supply ports 2 (left-and-right direction in FIGS. 1A and
1B), the order for discharging the ink colors onto a recording
medium (not shown) becomes the same, thereby preventing generation
of color unevenness.
As shown in enlarged views of FIGS. 2A and 2B illustrating left
side portions of FIGS. 1A and 1B, the large liquid droplet
discharge port 3a is provided at one side of each ink supply port 2
and the small liquid droplet discharge port 3b is provided at the
other side. The discharge ports 3a and 3b are communicated with a
common liquid chamber 6 via pressure chambers 4a and 4b and ink
flow paths 5a and 5b, respectively, and the common liquid chamber 6
is communicated with the ink supply ports 2. Electro-thermal
converting elements (referred to as "heaters" hereinafter) 7a and
7b are disposed within the pressure chambers 4a and 4b,
respectively. Incidentally, in this specification, the portion
including the ink flow path continued to the pressure chamber is
generically referred to as a "nozzle." A cylindrical nozzle filter
8 integrally formed with the discharge port plate 9 is disposed in
the vicinity of portions of the common liquid chamber 6 to which
the ink flow paths 5a and 5b are connected.
When it is assumed that a length of the nozzle for the large liquid
droplet is H.sub.L, a length of the nozzle for the small liquid
droplet is H.sub.S, a width of the nozzle for the large liquid
droplet (=width of large liquid droplet ink flow path 5a) is
W.sub.L and a width of the nozzle for the small liquid droplet
(=width of the small liquid droplet ink flow path 5b) is W.sub.S,
in this reference example, H.sub.L <H.sub.S and W.sub.L =W.sub.S
are satisfied. Thus, the flow resistance of the small liquid
droplet ink flow path 5b becomes great. Incidentally, the
dimensions of H.sub.L, H.sub.S, W.sub.L and W.sub.S are within a
range in which the flow resistance satisfies the following
relationships:
where S.sub.Lb : flow resistance of large liquid droplet side;
S.sub.Sb : flow resistance of small liquid droplet side; R.sub.Lf :
flow resistance from electro-thermal converting element of large
liquid droplet pressure chamber to corresponding discharge port;
R.sub.Lb : flow resistance from electro-thermal converting element
of large liquid droplet ink flow path to common liquid chamber;
S.sub.Le : effective bubbling area of the large liquid droplet
electro-thermal converting element; R.sub.Sf : flow resistance from
electro-thermal converting element of small liquid droplet pressure
chamber to corresponding discharge port; R.sub.Sb : flow resistance
from electro-thermal converting element of small liquid droplet ink
flow path to common liquid chamber; and S.sub.Se : effective
bubbling area of small liquid droplet electro-thermal converting
element.
Further, the flow resistances R.sub.f and R.sub.b are represented
by the following relationships or equations, respectively: ##EQU9##
D(x)=12.0.times.(0.33+1.02.times.(a(x)/b(x)+b(x)/a(x)))
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; D(x):
section coefficient of ink flow path at position of distance x;
a(x): height of ink flow path at position of distance x; b(x):
width of ink flow path at position of distance x; and .eta.: ink
viscosity, and, ##EQU10##
D(y)=12.0.times.(0.33+1.02.times.(c(y)/d(y)+d(y)/c(y)))
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from the common liquid chamber; S(y): sectional area of
ink flow path at position of distance y; D(y): section coefficient
of ink flow path at position of distance y; c(y): height of ink
flow path at position of distance y; and d(y): width of ink flow
path at position of distance y.
Further, when the flow resistances R.sub.f and R.sub.b are obtained
from dispersion calculations, the following relationships can be
obtained: ##EQU11##
D(x.sub.n)=12.0.times.(0.33+1.02.times.(a(x.sub.n)/b(x.sub.n)+b(x.sub.n)/
a(x.sub.n)))
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n): sectional area of ink flow
path at position of x.sub.n ; D(x.sub.n): section coefficient of
ink flow path at position of x.sub.n ; a(x.sub.n): height of ink
flow path at position of x.sub.n ; b(x.sub.n): width of ink flow
path at position of x.sub.n ; and .eta.: ink viscosity, and,
##EQU12##
D(y.sub.n)=12.0.times.(0.33+1.02.times.(c(y.sub.n)/d(y.sub.n)+d(y.sub.n)/
c(y.sub.n)))
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; S(y.sub.n): sectional area of ink flow path at position
of y.sub.n ; D(y.sub.n): section coefficient of ink flow path at
position of y.sub.n ; c(y.sub.n): height of ink flow path at
position of y.sub.n ; and d(x.sub.n): width of ink flow path at
position of y.sub.n.
Further, when the flow resistances are defined by inertance, the
following relationships are obtained: ##EQU13##
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; H: distance from
electro-thermal converting element to corresponding discharge port;
x: distance from electro-thermal converting element; S(x):
sectional area of ink flow path at position of distance x; and
.rho.: ink density, and, ##EQU14##
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; L: distance from center of
electro-thermal converting element to common liquid chamber; y:
distance from the common liquid chamber; and S(y): sectional area
of ink flow path at position of distance y.
Alternatively, the flow resistances can be represented by the
following equations: ##EQU15##
where R.sub.f : flow resistance from electro-thermal converting
element to corresponding discharge port; k: division number of
distance from electro-thermal converting element to corresponding
discharge port; x.sub.n : distance from electro-thermal converting
element to n-th division position when distance from
electro-thermal converting element to corresponding discharge port
is divided into k sections; S(x.sub.n): sectional area of ink flow
path at position of x.sub.n ; and .rho.: ink viscosity, and,
##EQU16##
where R.sub.b : flow resistance from electro-thermal converting
element to common liquid chamber; l: division number of distance
from center of electro-thermal converting element to common liquid
chamber; y.sub.n : distance from common liquid chamber to n-th
division position when distance from center of electro-thermal
converting element to common liquid chamber is divided into l
sections; and S(y.sub.n): sectional area of ink flow path at
position of y.sub.n.
Tests regarding the discharging of the large liquid droplet
(discharging amount of 5 pl) and the discharging of the small
liquid droplet (discharging amount of 2 pl) were actually performed
by using the ink jet recording head according to this reference
example, and a relationship between image quality experimentally
obtained (particularly, occurrence of a phenomenon in which the
discharging is distorted at random to form poor dots) and the flow
resistances S.sub.Sb and S.sub.Lb obtained by the calculations was
verified. Results are shown in the following Table 1. In this
reference example, the ink discharging was performed by a nozzle
No. 1 for discharging the large liquid droplet of 5 pl with nozzles
in which various conditions were changed. As shown in the Table 1,
an example in which two nozzles No. 1 for discharging the large
liquid droplet of 5 p1 are combined and examples in which the
nozzle No. 1 is combined with nozzles Nos. 2 to 5 for discharging
the small liquid droplet of 2 pl, respectively, were compared.
Incidentally, effective areas of the heaters 7a and 7b are sought
as follows. Since it is difficult to increase the temperature of
peripheral zones comprising 2 .mu.m margins at the edges of the
heaters 7a and 7b, and these zones thus do not contribute to the
bubbling, the effective area is calculated as an inside area
smaller than the actual size by 2 .mu.m. For example, the effective
area of each heater 7a or 7b having a size of 22.times.22 .mu.m is
(22-2.times.2).times.(22-2.times.2)=18.times.18=324 .mu.m.sup.2.
Further, a height of each ink flow path 5a or 5b of this ink jet
recording head is 14 .mu.m, and widths of the flow paths 5a and 5b
are W.sub.L =W.sub.S =32 .mu.m. Incidentally, R.sub.f is the
resistance of the discharge port 3a or 3b alone.
TABLE 1 Relationship between flow resistances S.sub.Lb, S.sub.Sb
and image quality NozzleNo. 1 2 3 4 5 Discharged Amount 5 2 2 2 2
(pl) Discharge Port 16 10.5 10.5 10.5 10.5 Diameter (.mu.m) Nozzle
Filter 10 10 10 10 15 Diameter (.mu.m) Heater Size (.mu.m) 26
.times. 26 26 .times. 26 24 .times. 24 22 .times. 22 26 .times. 26
Flow Resistance 199 384 317 257 262 S.sub.Lb, S.sub.Sb
(.mu.m.sup.2) S.sub.Sb /S.sub.Lb Ratio 1 1.93 1.59 1.29 1.32 Image
Quality .largecircle. X .DELTA. to .largecircle. .largecircle.
.largecircle.
As shown in the above Table 1, in the example in which two nozzles
No. 1 for the large liquid droplet are combined, poor printing such
as poor dot formation is not generated at all and image quality is
good.
In the example in which the nozzle No. 2 having a discharge port
diameter smaller than that of the nozzle No. 1 and adapted to
discharge the small liquid droplet of 2 pl is combined with the
nozzle No. 1, considerable poor dot formation was generated at the
nozzle No. 2 and the image quality was very bad. Incidentally, the
flow resistance S.sub.Sb of the nozzle No. 2 is greater than the
flow resistance S.sub.Lb of the nozzle No. 1 by 1.93 times.
In the examples in which the nozzle No. 3 having a heater size of
24.times.24 .mu.m smaller than that of the nozzle No. 2 and the
nozzle No. 4 having a smaller heater size of 22.times.22 .mu.m are
used, respectively, the poor dot formation was suppressed and the
image quality was enhanced. In the nozzle No. 3, in a certain case,
although slight poor dot formation was generated, in the nozzle No.
4, the poor dot formation was not generated at all and the image
quality was very good. Incidentally, S.sub.Sb /S.sub.Lb ratios of
the nozzles No. 3 and No. 4 are 1.59 and 1.29, respectively.
Further, in the example in which the nozzle No. 5 having a greater
diameter of the nozzle filter 8 than that of the nozzle No. 2 to
increase the flow resistance S.sub.Sb was used, the poor dot
formation was not generated so much and the image quality was good.
An S.sub.Sb /S.sub.Lb ratio thereof is 1.32.
From the above-mentioned results, it can be seen that, in order to
maintain a good discharging condition of the small liquid droplet,
it is important that escaping of the bubbling power toward the
direction of the common liquid chamber 6 is suppressed and that
cross-talk via the common liquid chamber 6 is suppressed.
Quantitatively, in order to suppress the calculated escaping amount
of the bubbling power toward the direction of the common liquid
chamber 6 to a predetermined amount or less, it is important that
various sizes are set on the basis of the above-mentioned
relationships or equations. The S.sub.Sb /S.sub.Lb ratio
corresponding to the escaping amount of the bubbling power from the
small liquid droplet ink flow path 5b to the common liquid chamber
6 must be below at least 1.93 and is more preferably smaller than
1.59. Further, according to the above-mentioned flow resistance
calculations, an absolute value of the flow resistance S.sub.Sb
must also be below 384 .mu.m.sup.2 and is more preferably smaller
than 317 .mu.m.sup.2.
As mentioned above, by determining the sizes of various parts and
the flow resistances on the basis of the above-mentioned
calculations, the cross-talk caused by the escaping of the bubbling
power toward the common liquid chamber 6 at the small liquid
droplet ink flow path 5b is reduced, with the result that the
liquid droplet discharging is stabilized to prevent poor recording
such as poor dot formation, thereby permitting high quality image
formation.
Second Reference Example
Next, an ink jet recording head according to a second reference
example will be explained with reference to FIGS. 3A and 3B.
Explanation of the same parts as those in the first reference
example will be omitted.
In this reference example, H.sub.L =H.sub.S and W.sub.L >W.sub.S
are satisfied. The sizes of various parts including W.sub.S are
sought by calculations similar to those in the first reference
example.
In the first reference example, although there is a problem that
the small liquid droplet ink flow paths 5b are lengthened and thus
the dimension of the entire ink jet recording head is increased, in
the second reference example, the flow resistances S.sub.Sb of the
small liquid droplet ink flow paths 5b can be increased without
increasing the dimension of the ink jet recording head.
First Embodiment
Next, a first embodiment of an ink jet recording head of the
present invention will be explained with reference to FIGS. 4A and
4B. Explanation of the same parts as those in the first and second
reference examples will be omitted.
In the first embodiment, H.sub.L =H.sub.S and W.sub.L >W.sub.S
are satisfied, and the width of the small liquid droplet ink flow
path 5b is smaller than the width of the small liquid droplet
pressure chamber 4b. That is to say, although the large liquid
droplet ink flow path 5a is directly connected to the large liquid
droplet pressure chamber 4a with the same width, the small liquid
droplet ink flow path 5b has the width smaller than that of the
small liquid droplet pressure chamber 4b, and, thus, restriction
for the ink flow is formed between the ink flow path and the
pressure chamber. Incidentally, the sizes of various parts are
determined by calculations similar to those in the first reference
example.
In the construction of the second reference example, the entire
width of the small liquid droplet ink flow path 5b is small to make
the configuration of the heater 4b narrower, thereby limiting the
size designing of the heater 4b, with the result that the driving
designing and the designing of the resistance of the heater film
are apt to be limited. Further, positional deviation of the nozzle
in a short side direction of the heater 4b easily affects an
influence upon the discharging direction. Further, there is a
problem that, if the effective bubbling area is changed due to long
term use, the change rate of the effective bubbling area becomes
great. To the contrary, in the first embodiment, the degrees of
freedom in the designing of the size of the heater 4b are great and
the degrees of freedom in the driving designing and the designing
of the heater film are great. Further, since the configuration of
the heater can be selected as a square, the influence of positional
deviation of the nozzle on the discharge direction can be
minimized, with the result that the change rate of the effective
bubbling area during long term use can be minimized. The other
aspects of construction are similar to those in the first reference
example.
Second Embodiment
Next, a second embodiment of an ink jet recording head of the
present invention will be explained with reference to FIGS. 5A and
5B. Explanation of the same parts as those in the first and second
reference examples and the first embodiment will be omitted.
In the second embodiment, the diameter of nozzle filter 8
corresponding to the small liquid droplet ink flow path 5b is
great. The other aspects of construction are the same as those in
the first embodiment. The sizes of various parts including the
dimensions of the nozzle filter 8 are sought by calculations
similar to those in the first reference example.
In the second embodiment, even when the width W.sub.S of the small
liquid droplet ink flow path 5b is not narrowed extremely, the flow
resistance S.sub.Sb can be increased and optimized by making the
nozzle filter 8 larger. Accordingly, there is little influence of
manufacturing tolerance of the ink flow path 5b, and it is hard for
the dispersion in the flow resistances S.sub.Sb of the nozzles for
the small liquid droplet to be so great. Further, since the width
W.sub.S of the small liquid droplet ink flow path 5b is not so
narrow and the nozzle filter 8 is large, it is hard for dirt or
debris to cause clogging.
Third Reference Example
Next, an ink jet recording head according to a third reference
example will be explained with reference to FIGS. 6A and 6B.
Explanation of the same parts as those in the first and second
reference examples will be omitted.
In this reference example, the small liquid droplet nozzles and the
large liquid droplet nozzles are alternately disposed in the same
column. The other aspects of construction are the same as those in
the first reference example.
In this reference example, since the distance between the large
liquid droplet ink flow paths 5a and the distance between the small
liquid droplet ink flow paths 5b can be widened, cross-talk and the
influence of air flow between the large liquid droplet ink flow
paths 5a or between the small liquid droplet ink flow paths 5b
caused when high speed printing is performed by using only the
large liquid droplets or the small liquid droplets can be reduced,
thereby stabilizing the discharging and permitting high speed
printing of a high quality image.
Fourth Reference Example
Next, an ink jet recording head according to a fourth reference
example will be explained with reference to FIGS. 7A and 7B.
Explanation of the same parts as those in the first to third
reference examples will be omitted.
In this reference example, the small liquid droplet nozzles and the
large liquid droplet nozzles are alternately disposed in the same
column. The other aspects of construction are the same as those in
the second reference example. Accordingly, similar to the third
reference example, cross-talk and the influence of the air flow
caused when high speed printing is performed by using only the
large liquid droplets or small liquid droplets can be reduced,
thereby stabilizing the discharging and permitting high speed
printing of a high quality image. Further, similar to the second
reference example, the flow resistances S.sub.Sb of the small
liquid droplet ink flow paths 5b can be increased without
increasing the size of the ink jet recording head.
Third Embodiment
Next, a third embodiment of an ink jet recording head of the
present invention will be explained with reference to FIGS. 8A and
8B. Explanation of the same parts as those in the first to fourth
reference examples and the first and second embodiments will be
omitted.
In the third embodiment, the small liquid droplet nozzles and the
large liquid droplet nozzles are alternately disposed in the same
column. The other aspects of construction are the same as those in
the first embodiment. Accordingly, similar to the first embodiment,
the degrees of freedom in designing the size of the heater 4b are
great, with the result that the influence of positional deviation
of the nozzle on the discharging direction can be minimized and
that the change rate of the effective bubbling area during long
term use can be minimized. Further, similar to the fourth reference
example, cross-talk and the influence of the air flow caused when
high speed printing is performed by using only the large liquid
droplets or small liquid droplets can be reduced, thereby
stabilizing the discharging and permitting high speed printing of a
high quality image, and further, the flow resistances S.sub.Sb of
the small liquid droplet ink flow paths 5b can be increased without
increasing the size of the ink jet recording head.
Fourth Embodiment
Next, a fourth embodiment of an ink jet recording head of the
present invention will be explained with reference to FIGS. 9A and
9B. Explanation of the same parts as those in the first to fourth
reference examples and the first to third embodiments will be
omitted.
In the fourth embodiment, the small liquid droplet nozzles and the
large liquid droplet nozzles are alternately disposed in the same
column and the diameter of the nozzle filter 8 corresponding to the
small liquid droplet ink flow path 5b is great. The other aspects
of construction are the same as those in the second embodiment.
Accordingly, similar to the first embodiment, the degrees of
freedom in designing the size of the heater 4b are great, with the
result that the influence of positional deviation of the nozzle on
the discharging direction can be minimized and that the change rate
of the effective bubbling area during long term use can be
minimized. Further, similar to the fourth reference example,
cross-talk and the influence of the air flow caused when high speed
printing is performed by using only the large liquid droplets or
small liquid droplets can be reduced, thereby stabilizing the
discharging and permitting high speed printing of a high quality
image, and further, the flow resistances S.sub.Sb of the small
liquid droplet ink flow paths 5b can be increased without
increasing the size of the ink jet recording head. Further, similar
to the second embodiment, it is hard for the dispersion in the flow
resistances S.sub.Sb of the nozzles for the small liquid droplet to
be so great and thus it is hard for dirt to cause clogging.
Fifth Embodiment
Next, a fifth embodiment of an ink jet recording head of the
present invention will be explained with reference to FIGS. 10A and
10B. Explanation of the same parts as those in the first to fourth
reference examples and the first to fourth embodiments will be
omitted.
In the fifth embodiment, the width of the small liquid droplet ink
flow path 5b is narrower than the width of the small liquid droplet
pressure chamber 4b and the width of the large liquid droplet ink
flow path 5a is narrower than the width of the large liquid droplet
pressure chamber 4a so that both the small liquid droplet ink flow
path 5b and the large liquid droplet ink flow path 5a act as
restriction portions for the ink flow. That is to say, if it is
assumed that the width of the large liquid droplet pressure chamber
is W.sub.RL, the width of the large liquid droplet ink flow path is
W.sub.L, the width of the small liquid droplet pressure chamber is
W.sub.RS and the width of the small liquid droplet ink flow path is
W.sub.S, W.sub.RL.congruent.W.sub.RS and W.sub.L >W.sub.S and
W.sub.S /W.sub.RS <W.sub.L /W.sub.RL are satisfied. The other
aspects of construction are the same as those in the first
embodiment. Accordingly, in not only the small liquid droplet ink
flow paths 5b but also the large liquid droplet ink flow paths 5a,
the flow resistances can be increased without increasing the size
of the ink jet recording head. Further, the degrees of freedom in
designing the sizes of the heaters 4a and 4b are great, with the
result that the influence of positional deviation of the nozzle on
the discharging direction can be minimized and that the change rate
of the effective bubbling area during long term use can be
minimized.
Example
The inventors manufactured many nozzles and judged the recording
properties thereof, the results of which are shown in the following
Table 2. The nozzles which were able to achieve good recording are
shown by Nos. 4 to 27. Their heater sizes, pressure chambers and
pressure chamber widths are given in Table 2. Further, nozzles Nos.
1 to 3 show reference designing examples where the heater size
could be reduced.
TABLE 2 Embodiment 1 Embodiment 2 Embodiment 3 Heater (12.5 .times.
28) .times. 2 Heater 26 .times. 26 Heater 30 .times. 30 Discharged
Amount Discharged Amount Discharged Amount Sample Nozzle 5.4 (pl)
5.4 (pl) 8.5 (pl) Dis- Pressure charged Heater Chamber Pressure
Chamber Pressure Chamber Pressure Chamber Amount Total Bottom
Bottom Width Bottom Width Bottom Width No. (pl) Size Area Area
Width Area Ratio Ratio Area Ratio Ratio Area Ratio Ratio 1 0.5 12
.times. 12 144 256 16 0.25 0.50 0.28 0.53 0.22 0.47 2 0.5 13
.times. 13 169 289 17 0.28 0.53 0.32 0.57 0.25 0.50 3 0.5 14
.times. 14 196 324 18 0.32 0.56 0.36 0.60 0.28 0.53 4 0.5 16
.times. 16 256 400 20 0.39 0.63 0.44 0.67 0.35 0.59 5 0.5 17
.times. 17 289 441 21 0.43 0.66 0.49 0.70 0.38 0.62 6 0.5 18
.times. 18 324 484 22 0.47 0.69 0.54 0.73 0.42 0.65 7 0.5 19
.times. 19 361 529 23 0.52 0.72 0.59 0.77 0.46 0.68 8 1.0 20
.times. 20 400 576 24 0.56 0.75 0.64 0.80 0.50 0.71 9 1.0 21
.times. 21 441 625 25 0.61 0.78 0.69 0.83 0.54 0.74 10 2.4 22
.times. 22 484 676 26 0.66 0.81 0.75 0.87 0.58 0.76 11 2.4 23
.times. 23 529 729 27 0.71 0.84 0.81 0.90 0.63 0.79 12 2.4 20
.times. 24 480 672 24 0.66 0.75 0.75 0.80 0.58 0.71 13 2.4 (11.5
.times. 27) .times. 2 621 930 30 0.91 0.94 1.03 1.00 0.80 0.88 14
4.5 24 .times. 24 576 784 28 0.77 0.88 0.87 0.93 0.68 0.82 15 4.5
25 .times. 25 625 841 29 0.82 0.91 0.93 0.97 0.73 0.85 16 5.4 26
.times. 26 676 900 30 0.88 0.94 1.00 1.00 0.78 0.88 17 5.4 27
.times. 27 729 961 31 0.94 0.97 1.07 1.03 0.83 0.91 18 5.4 (12.5
.times. 28) .times. 2 700 1,024 32 1.00 1.00 1.14 1.07 0.89 0.94 19
8.5 28 .times. 28 784 1,024 32 1.00 1.00 1.14 1.07 0.89 0.94 20 8.5
29 .times. 29 841 1,089 33 1.06 1.03 1.21 1.10 0.94 0.97 21 8.5 30
.times. 30 900 1,156 34 1.13 1.06 1.28 1.13 1.00 1.00 22 8.5 31
.times. 31 961 1,225 35 1.20 1.09 1.36 1.17 1.06 1.03 23 8.5 32
.times. 32 1,024 1,296 36 1.27 1.13 1.44 1.20 1.12 1.06 24 8.5 33
.times. 33 1,089 1,369 37 1.34 1.16 1.52 1.23 1.18 1.09 25 8.5 34
.times. 34 1,156 1,444 38 1.41 1.19 1.60 1.27 1.25 1.12 26 8.5 35
.times. 35 1,225 1,521 39 1.49 1.22 1.69 1.30 1.32 1.15 27 8.5 36
.times. 36 1,296 1,600 40 1.56 1.25 1.78 1.33 1.38 1.18
* * * * *